If the return value of a command is greater than 128, it means that the command is terminated by signal.
$ man bash
The return value of a simple command is its exit status, or 128+n if the command is terminated by signal n.
$ some_command $ echo $? 139
In the above example, the return value is 139. Because 139=128+11 it means that the command was terminated by signal 11.
See `man signal` and you will find that signal 11 is SIGSEGV and it means segmentation violation.